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Biomedical subjects

B Zhao

Publications and source records attributed to B Zhao.

At least 181 records · Page 10Linked to original sources
PubMed1996

A conserved domain of the Epstein-Barr virus nuclear antigens 3A and 3C binds to a discrete domain of Jkappa.

EBNA-3C can affect the LMP-1 promoter in both a positive and a negative manner through distinct DNA sequence elements. The viral transactivator EBNA-2 normally binds DNA indirectly via Jkappa to activate transcription, but this activation is prevented in the presence of EBNA-3C. The DNA element recognized by Jkappa is both required and sufficient for this inhibition. Jkappa clones isolated in a yeast two-hybrid screen using EBNA-3C as bait allowed us to delineate the sequences of both proteins mediating the interaction. Two isoforms of Jkappa that differ in exon 1, Jkappa-1 and RBP-2N, interact with EBNA-3C, suggesting that exon 1 is not required for this interaction; indeed, clones with deletion of the N-terminal third of Jkappa interacted as efficiently with EBNA-3C as full-length Jkappa clones. A Jkappa domain as small as 56 amino acids was sufficient to bind to EBNA-3C. A 74-amino-acid domain of EBNA-3C, conserved in all three EBNA-3 family members, was sufficient to interact with Jkappa. A specific mutation in this conserved domain suppressed the ability of EBNA-3C to downregulate transcription. Accordingly, EBNA-3A was also able to interact with Jkappa and downregulate Jkappa-mediated transcription as efficiently as EBNA-3C. The ability of the EBNA-3 proteins to prevent Jkappa from binding to DNA in vitro and suppress transactivation via Jkappa DNA elements suggests that the EBNA-3 proteins act analogously to the Drosophila protein Hairless.

Antigens, Viral↗
PubMed1996

Qualitative investigations on vital blood platelets by reflection contrast microscopy.

Light-microscopic visualization of vital human blood platelets is improved by reflection contrast microscopy. The light reflected from the specimen causes interference patterns which are used for the assessment of surfaces or adhesion areas. By means of this technique we studied the activation process of unstimulated platelets. During the observation the following two features were assessed: (1) Platelet adhesion areas and their shape change: two main types of adhesion patterns were found for activated platelets. Type A was characterized by flat spreading and extensive adhesion zones, whereas type B showed only focal contacts in the center and long and sometimes dichotomously split pseudopodia. Both adhesion types coexisted in each sample but did not change into one another during the observation period of 25 min. (2) Pseudopodia formation: initially, a rapid evagination of mobile pseudopodia could be observed which lasted for approximately 2 min. After reaching their final individual length, the pseudopodia adhered to the glass and remained stationary.

Blood Platelets↗
PubMed1996

A strongly inwardly rectifying K+ channel that is sensitive to ATP.

We have cloned an inwardly rectifying K+ channel from the hamster insulinoma cDNA library and shown that it is inhibited by cytoplasmic ATP. The channel is 90.97% identical to the IRK3 channels cloned from other species, and its mRNA is found primarily in the brain. When expressed in Xenopus oocytes, the channel displays strong inward rectification typical of inward rectifiers. The channel is inhibited reversibly by physiological concentrations of ATP via a mechanism that does not appear to involve ATP hydrolysis, as shown by studies of channels in excised inside-out membrane patches. This effect is antagonized by ADP, again in the physiological range, implying that this channel is sensitive to the index of metabolic state, i.e., the intracellular [ATP]/[ADP] ratio. This channel is different from previously known ATP-sensitive K+ channels, although it may also be stimulated by MgATP, as are other ATP-sensitive K+ channels. The potential physiological significance of these ATP-dependent regulations will be discussed.

Adenosine Diphosphate↗
PubMed1996

[A PCR marker-based selection for resistance to bacterial blight in rice].

Molecular marker-based selection in plant breeding requires not only suitable molecular markers closely linked to the known genes, but a simple, economic and reliable analyzing technique. We report here a useful PCR marker for genetic diagnostics in breeding for resistance to rice bacterial blight. Xa21 is a newly found gene of rice which confers resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae. We produced two F2 populations between one resistant line IRBB21 containing Xa21 and two susceptible varieties, respectively. One PCR marker, PB78, detected polymorphism between the susceptible varieties and the resistant line. Cosegregation between Xa21 and PB78 was studied in the two F2 populations. The results showed that Xa21 was closely linked to the molecular marker, the crossing over value was 2.48%. Marker-based selection revealed that 100% of the plants with homozygous resistant genotype of PB78 showed resistance to bacterial blight. The available approaches detecting molecular markers in plant breeding are also discussed.

Base Sequence↗
PubMed1996

[Treatment of neovascular glaucoma by anterior retinal cryotherapy and trabeculectomy].

OBJECTIVE: To investigate the efficacy of anterior retinal cryotherapy (ARC) for treatment of neovascular glaucoma (NVG). METHODS: 12 eyes (11 patients) with open angle NVG were treated by ARC only, 22 eyes (22 patients) with closed angle NVG were treated by ARC combined with trabeculectomy, and 32 eyes (31 patients) with closed angle NVG were treated by either ARC or cyclocryotherapy as controls. The follow-up period were 6-26 months. RESULTS: Iris new vessels (INV) regressed or disappeared with normal intraocular pressure (IOP) in 92% (11/12) of the eyes with open angle NVG treated simply by ARC. In comparison with closed angle NVG treated by the same method, there was a significant difference in IOP (P < 0.05). The combination of ARC and trabeculectomy showed markedly better results than either ARC or cyclocryotherapy for treatment of closed angle NVG (P < 0.01). In the eyes with closed angle NVG, INV regressed or disappeared with normal IOP in 86% (19/22), 90% (18/20) achieved a marked relief from pain and the visual acuity was better or unchanged in 67% (8/12) that was significantly different from the eyes treated by cyclocryotherapy (P < 0.05). CONCLUSION: The results indicate that ARC is suitable for treatment of NVG at early stage, and ARC combined with trabeculectomy, at later stage.

Adult↗
PubMed1996

Effects of nicotinamide on prevention and treatment of streptozotocin-induced diabetes mellitus in rats.

OBJECTIVE: To study the effect of nicotinamide (NAA) on prevention and treatment of STZ-induced diabetes mellitus in rats. MATERIAL AND METHODS: 30 Sprague-Dawley rats were randomly divided inot three groups: 20 rats were given NAA 1 g/kg/day intramuscularly (10 rats) or orally (10 rats) as experimental groups and the other 10 rats by normal saline orally as control group. Three days later, all 30 rats received streptozotocin (STZ) 55 mg/kg by intraperitioneal injection and took NAA or normal saline continuously as described above for 14 days. During the study, fasting blood glucose (FBG) was measured before and 72 hours after STZ injection and every 2-3 days later on with Glucometer, 24 hours urinary glucose excretion (UGE) was determined once every 4 days with glucose oxidase, body weight was determined every week, the volume of 24-hour water intake and urine excretion were determined twice and once a week respectively. RESULTS: Two weeks after STZ injection, FBG and 24 hours UGE of all rats taking NAA were normal or nearly normal, islet function and morphology revealed no significant differences compared with those of the normal, whereas all rats of control group remained hyperglycemic (> 16.6 mmol/L) and markedly higher 24 hours UGE as compared with the normal islets appeared atrophic with decrement of B cell population. CONCLUSIONS: The results showed that NAA may effectively prevent the occurrence of STZ-induced diabetes mellitus in rats, suggesting that NAA may be an effective agent for prevention and treatment of insulin-dependent diabetes mellitus (IDDM) in prediabetic and early stage of IDDM.

Animals↗
PubMed1996

Synergic effects of NO and oxygen free radicals in the injury of ischemia-reperfused myocardium--ESR studies on NO free radicals generated from ischemia-reperfused myocardium.

The ESR signal of NO bound to hemoglobin was detected during the ischemia-reperfusion of myocardium with low temperature ESR technique, and the synergic effects of NO and oxygen free radicals in the injury of the process were studied with this technique. Oxygen free radicals and NO bound to beta-subunit of hemoglobin (beta-NO complex) could be detected simultaneously in the ischemia-reperfused myocardium. Those signals could not be detected from the normal myocardium even in the presence of L-arginine. However, those signals could be detected and were dose-dependent with L-arginine in the ischemia-reperfused myocardiums and the signal could be suppressed with the inhibitor of NO synthetase, NG-nitro-L-arginine methylester (NAME). Measurement of the activities of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary artery effluent of ischemia-reperfused heart showed that L-arginine at lower concentration (< 1 mmol/L) could protect the heart form the ischemia-reperfusion injury but at higher concentration aggravate the injury. Addition of NAME to the reperfusion solution could also protect the myocardium. Addition of xanthine (X)/xanthine oxidase (XO) or Fe2+/H2O2 to the reperfusion solution increased the production of NO and oxygen free radicals and the ischemia-reperfused injury simultaneously. Addition of superoxide dismutase (SOD) and catalase decreased the production of NO and oxygen free radicals and the ischemia-reperfusion injury.

Animals↗
PubMed1996

[Determination of puerarin in gegen ginlian tablets by RP-HPLC].

A quantitative method was developed for the determination of puerarin in Gegen Qinglian Tablets by reversed phase HPLC. Chromatographic conditions included column ODS-C18, column temperature: 35 C, UV detector: 250 nm, mobile phase: EtOH-H2O (23:77), flow rate: 1 ml/min. The number of theoretical plates calculated for puerarin peak was no less than 2000. The standard curve was linear in the concentration range of 5-80 micrograms/ml, and the correlation coefficient was 0.9999. The average recovery and the relative standard deviation were 97.6% and 1.8% respectivily.

Chromatography, High Pressure Liquid↗
PubMed1995

In vivo analysis of straight-chain and branched-chain fatty acid biosynthesis in three actinomycetes.

The starter units for branched-chain and straight-chain fatty acid biosynthesis was investigated in vivo in three actinomycetes using stable isotopes. Branched-chain fatty acids, which constitute the majority of the fatty acid pool, were confirmed to be biosynthesized using the amino acid degradation products methylbutyrl-CoA and isobutyrl-CoA as starter units. Straight-chain fatty acids were shown to be constructed using butyrl-CoA as a starter unit. Isomerization of the valine catabolite isobutyryl-CoA was shown to be only a minor source of this butyryl-CoA.

Acyl Coenzyme A↗
PubMed1995

A check on rational drug design: crystal structure of a complex of human immunodeficiency virus type 1 protease with a novel gamma-turn mimetic inhibitor.

We have previously reported (Newlander et al., J. Med. Chem. 1993, 36, 2321-2331) the design of human immunodeficiency virus type 1 (HIV-1) protease inhibitors incorporating C7 mimetics that lock three amino acid residues of a peptide sequence into a gamma-turn. The design of one such compound, SB203238, was based on X-ray structures of reduced amide aspartyl protease inhibitors. It incorporates a gamma-turn mimetic in the P2-P1' position, where the carbonyl of the C7 ring is replaced with an sp3 methylene group yielding a constrained reduced amide. It shows competitive inhibition with Ki = 430 nM at pH 6.0. The three-dimensional structure of SB203238 bound to the active site of HIV-1 protease has been determined at 2.3 A resolution by X-ray diffraction and refined to a crystallographic R-factor (R = sigma magnitude of Fo magnitude of - magnitude of Fc magnitude of /sigma magnitude of Fo magnitude of, where Fo and Fc are the observed and calculated structure factor amplitudes, respectively) of 0.177. The inhibitor lies in an extended conformation in the active site; however, because of the constrained geometry of the C7 ring, it maintains fewer hydrogen bonds with the protein than in most other HIV-1 protease-inhibitor complexes. More importantly, the inhibitor binds to the enzyme differently than predicted in its design, by binding with the P2-P1' alpha-carbon atoms shifted by approximately one-half a residue toward the N-terminus from their presumed positions. This study illustrates the importance of structural information in an approach to rational drug design.

Amino Acid Sequence↗
PubMed1995

Binding interactions of human interleukin 5 with its receptor alpha subunit. Large scale production, structural, and functional studies of Drosophila-expressed recombinant proteins.

Human interleukin 5 (hIL5) and soluble forms of its receptor alpha subunit were expressed in Drosophila cells and purified to homogeneity, allowing a detailed structural and functional analysis. B cell proliferation confirmed that the hIL5 was biologically active. Deglycosylated hIL5 remained active, while similarly deglycosylated receptor alpha subunit lost activity. The crystal structure of the deglycosylated hIL5 was determined to 2.6-A resolution and found to be similar to that of the protein produced in Escherichia coli. Human IL5 was shown by analytical ultracentrifugation to form a 1:1 complex with the soluble domain of the hIL5 receptor alpha subunit (shIL5R alpha). Additionally, the relative abundance of ligand and receptor in the hIL5.shIL5R alpha complex was determined to be 1:1 by both titration calorimetry and SDS-polyacrylamide gel electrophoresis analysis of dissolved cocrystals of the complex. Titration microcalorimetry yielded equilibrium dissociation constants of 3.1 and 2.0 nM, respectively, for the binding of hIL5 to shIL5R alpha and to a chimeric form of the receptor containing shIL5R alpha fused to the immunoglobulin Fc domain (shIL5R alpha-Fc). Analysis of the binding thermodynamics of IL5 and its soluble receptor indicates that conformational changes are coupled to the binding reaction. Kinetic analysis using surface plasmon resonance yielded data consistent with the Kd values from calorimetry and also with the possibility of conformational isomerization in the interaction of hIL5 with the receptor alpha subunit. Using a radioligand binding assay, the affinity of hIL5 with full-length hIL5R alpha in Drosophila membranes was found to be 6 nM, in accord with the affinities measured for the soluble receptor forms. Hence, most of the binding energy of the alpha receptor is supplied by the soluble domain. Taken with other aspects of hIL5 structure and biological activity, the data obtained allow a prediction for how 1:1 stoichiometry and conformational change can lead to the formation of hIL5.receptor alpha beta complex and signal transduction.

Amino Acid Sequence↗
PubMed1995

Regulation of rat ornithine decarboxylase promoter activity by binding of transcription factor Sp1.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme of polyamine biosynthesis. We investigated the transcriptional regulation of the rat ODC gene using transient expression assays. The 5'-flanking region (-1156 to +13) of the ODC gene was sufficient to mediate strong basal expression of a luciferase reporter. Sequences between -345 and -93 contributed to basal promoter activity. This region, containing five potential Sp1 binding sites, was analyzed by electrophoretic mobility shift assays. Three specific DNA-protein complexes were identified using H35 nuclear extracts and the -345/-93 ODC probe. Binding to all three was eliminated by competition with an oligonucleotide containing an Sp1 binding site, but not by a mutant Sp1 oligonucleotide. Preincubation with an antibody against Sp1 supershifted complexes associated with one or more of Sp1 binding sites 1-4 as well as with site 5. DNase I footprinting revealed two protected regions: PR-I (-92 to -130) and PR-II (-304 to -332). PR-I contains a putative binding site for Sp1 that was protected by recombinant Sp1 protein. Transfection studies in Schneider SL2 cells demonstrated that the ODC promoter is transactivated up to 350-fold by Sp1 and that this transactivation is dependent on the presence of Sp1 binding sites 1-4. Thus, although the ODC promoter binds multiple nuclear proteins, Sp1 or a related protein appears to be a critical determinant of ODC transcription, possibly through cooperative interactions between Sp1 and additional transcription factors.

Animals↗
PubMed1995

Requirement of MADS domain transcription factor D-MEF2 for muscle formation in Drosophila.

Members of the myocyte enhancer binding factor-2 (MEF2) family of MADS (MCM1, agamous, deficiens, and serum response factor) box transcription factors are expressed in the skeletal, cardiac, and smooth muscle lineages of vertebrate and Drosophila embryos. These factors bind an adenine-thymidine-rich DNA sequence associated with muscle-specific genes. The function of MEF2 was determined by generating a loss-of-function of the single mef2 gene in Drosophila (D-mef2). In loss-of-function embryos, somatic, cardiac, and visceral muscle cells did not differentiate, but myoblasts were normally specified and positioned. These results demonstrate that different muscle cell types share a common myogenic differentiation program controlled by MEF2.

Animals↗
PubMed1995

Altered processing of a mutant amyloid precursor protein in neuronal and endothelial cells.

Altered proteolysis of the amyloid precursor protein (APP) may play an important role in Alzheimer disease (AD). To better understand the role of mutant APP in the pathogenesis of the disease, we stably overexpressed the mutant APP717F approximately twofold vs. the endogenous wild-type gene in several cell types. The processing of APP was examined by Western blot analysis and immunoprecipitation. We observed distinctive patterns of APP metabolites among various cell lines. Neuronal and endothelial cells expressing mutant APP717F generated higher levels of large, potentially amyloidogenic carboxyl terminal fragments, which were enhanced upon treatment of the cells with leupeptin. These results suggest that mutations in the APP gene shift the protein processing towards the amyloidogenic pathway in neuronal and endothelial cells possibly involving the endosomal-lysosomal system.

Alzheimer Disease↗
PubMed1995

Pneumococcal clearance function of the intact autotransplanted spleen.

OBJECTIVE: To determine if the venous drainage of the spleen into the portal circulation is essential for its ability to protect against encapsulated bacterial challenge. DESIGN AND INTERVENTIONS: Three groups of dogs were randomly assigned to undergo either sham laparotomy, splenectomy, or splenectomy with autotransplantation of the intact spleen into the pelvis and formation of vascular anastomoses to the iliac vessels. Two weeks post-operatively, the dogs received a sublethal intravenous injection of Streptococcus pneumoniae type 25. OUTCOME MEASURES: Bacterial clearances and inflammatory damage to the liver. Bacterial clearance of the autotransplanted spleen should be no different from that of a sham-operation spleen and significantly different from that of a splenectomized animal. In addition, immunologic function of the autotransplanted spleen should not differ from that of a sham-operation spleen in the degree of inflammatory damage to the liver. RESULTS: No differences in bacterial clearance function were found between the animals that had undergone sham laparotomy or splenic autotransplantation. However, bacterial clearance in the splenectomized animals was significantly impaired. Histologic examination of the liver 2 weeks after the bacterial challenge revealed high-grade inflammatory damage to the livers of splenectomized dogs, intermediate liver damage in dogs that underwent autotransplantation, and essentially no damage in dogs that underwent sham laparotomy. Autotransplanted spleens were essentially nonreactive, lacking actively proliferating germinal centers, whereas splenic tissue from sham-operation animals showed reactivity. CONCLUSION: Although bacterial clearance function is unchanged in autotransplanted spleens, this method still does not fully protect the liver from inflammatory damage.

Analysis of Variance↗
PubMed1995

Oxidized LDL induces serotonin release from blood platelets.

Oxidized low-density lipoprotein (LDL) induces a release of serotonin from morphologically resting platelets and shape changed platelets. This suggests that oxidized LDL, a newly reported weak agonist, contributes to atherogenesis and thrombogenesis by stimulating platelets.

Blood Platelets↗
PubMed1995

Adhesion of washed blood platelets in vitro is advanced, accelerated, and enlarged by oxidized low-density lipoprotein.

In order to study the influence of oxidized low-density lipoprotein (Ox-LDL) on platelet functional morphology at an early activation stage, washed human blood platelets were stimulated by 100 micrograms/ml Ox-LDL at 37 degrees C. The settling and spreading process of stimulated and unstimulated platelets on Formvar-coated glass was observed for approximately 20 min by reflection contrast microscopy (RCM) and quantified by image analysis. Each group consisted of at least 250 platelets. The results show that incubation with Ox-LDL causes platelet shape change and pseudopodia formation. The sedimentation of stimulated platelets precedes that of unstimulated platelets by approximately 3 min. The increase of the total adhesion area of all Ox-LDL treated platelets is significantly accelerated in comparison to normal platelets (20.45 microns2/min vs. 15.45 microns2/min; P < 0.01). The mean total adhesion area of Ox-LDL-treated platelets was generally larger than that of untreated platelets (189.7 microns2 vs. 144.7 microns2; P < 0.01). The disappearance of intracellular granules after platelet activation, observed by RCM, is supported by transmission electron microscopy. Our results suggest that Ox-LDL activates platelets and advances and accelerates their adhesion and thereby may contribute to pathological thrombosis and arteriosclerosis.

Blood Platelets↗